Anyone using a Crower 52242 Compu Pro camshaft ..

Nick

I'm all out of epiphanies. I would love nothing more than to spend my days in a Dyno room investigating problems like this one and coming up with answers and solutions. There are also some concepts that need to be pushed further, along with new engine designs. Need more funding!

Cam flexing and valve train component flexing at this level (5000-5500 rpm) can cause a small decrease in duration and valve lift but I don't see that the engines ability to make power would be decreased by anything significant certainly not to the point of rev limiting.
That is usually valve float or hyd lifter pump down.

If a person wanted to verify this in a BBB that was having a problem with a high ramp rate cam, they would first install solid lifters and use 16 adjustable pushrods (Stock rocker arms) to set the valve clearance. If the problem repeats then change to heavier valve springs.
if that fixes it then put the hyd lifters back in and see if it stays fixed or the lifter are also part of the problem.

In the dyno room there would be linear transducers at various locations on the valve train so you could see all the points of instabilities at different rpms.
then you could also include valve train mass reduction and see if there is an economical combination of components that allow the use of high ramp angle cams with hyd lifters in the BBB.

Paul

 

Thanks for the input Paul, I have come to terms with my fast lobe profile problems, if they don't show major gains over the slower profile cams with the same lift & dur then I will no longer be useing them. It's not worth the extra cash spent for mech lifters & adj pushrods or roller rockers just to say I run a fast profile camshaft. Paul here are my port flow rates between .100 & .500

.100 .200 .300 .400 .500 lift
69 138 202 244 254 in.
57 109 147 171 184 ex. w/o header flow tube

83% 79% 73% 70% 72%

I talked to Dave @ Crower today & got info on a couple grinds ,he said he felt the heads would suport less in/ex dur spread with no problem .

Thanks , this has been a great thread so far.

Mark

 

Mark

Dave or Guy will set you up with what you need.
Good mid range numbers.
It's nice to be able to use less of a duration spread.
Less overlap for better intake manifold vacuum. Makes it a lot easier to tune the carb for idle and off idle.

What were some of the grinds Dave was looking at?

Paul

 

I was thinking(scary i know lol)

It appears he is only lookig to pick up 300-400 usable rpm'
I wonder where else to look for it besides automatically saying he needs a cam change to do it
If there is possibly a valvetrain issue ,that is currently present,and causing issues,once you change cams,wont you still be masking a problem that ,onced resolved ,will produce more overall power anyhow?
Again,just thinking out loud is all

 

a fast ramp cam is a poor mans roller cam, better idle and more vacuum, greater power curve. you will most likely be giving up 15hp. i have a 1987 paw catalog showing that same came number and profile. thats at least a 26 year old design. the extreme energy is not really that fast a ramp now a days, but tons faster then the crower.

 

Here is the baseline flat tappet that will get are lift figures : 310* / 316* adv dur. @.050 252* / 258* 108* Lsa lift @ TDC .197'' / .158'' Idle @ 1100 -1200 lumpy est 503.94 @ 5500 hp / 587.94 @4557 TQ.
Well for shure this is to large a camshaft for my combo ,but it is just a starting point to draw from to come up with the best grind , for my combo. Dave said to give him a call & we can get down to the bottom line on specs.

Paul , looking @ the cam specs above I find it hard to think this cam would pull hard @ 2500 rpm ,i am thinking more in the 230* 234* intake dur range.

Mark

 

Thats a pretty large cam for what you are trying to accomplish :shock:

 

You are correct. Too big for what you want to do. With 39 degrees overlap the exhaust fumes at idle will drive you out of the garage in a hurry.
The power won't come on till after 3000 rpm.

Yes you are looking at low to mid 230s intake duration at the most. 110 LSA would be a good compromise between track and street manners.
I think you have it down.

What I would like to see is 234/240 duration, lobe lift .335, 110 LSA.
I wanted a 6 degree spread because the port flow ratio dips low (70%) at .400 lift. Just a little extra help for that region.
17 degrees of overlap is still reasonable for intake manifold vacuum. Inital timing will need to be around 20 degrees BTDC.

Keep us posted

Paul

 

Why not something like 227-242 on 108 l/s installed at 106 or maybe even straight up
Only need 5500 rpm so why not keep the intake lobe down,and let it pull up top a little more with the exh hung out so to speak
I think people waaaayyyy over cam the intake side of things IMO

 

Because the port flow ratio on his level 3 heads don't require a large spread on the duration to completely evacuate the cylinder of exhaust.
All you are doing is unnecessarily increasing overlap.
The 110 LSA is a nice compromise between track and street drivability.
108 LSA is for Denver

Paul

 

what do your heads flow at .500 and .600 lift ?

 

260/190 @ .550 is the only other number

 

like to see .500-.600.maybe theres no reason to run .550 lift. theres a lot more choices at about .525 lift out there, with a lower duration number. the cam 226-230 on 109 LSA with 106 CL. but with a faster ramp then crower to get the advertise duration down for a better idle and low end. it should pull to the very least 5500-5700 rpm . maybe with the 9.5 converter and the big cubes it will come on at 2600-2800 rpm. 2500 would be tough. why does it have to be a crower cam?. any flat tappet cam should be nitride now a days.

 

That is a big cam for sure ! There is a reason for that .... I made a mistake & hit the roller cam button, Dave said if those specs were to be on a flat tappet the lifter would have to be 1'' in dia LOL

I will post when he gets back to me on the Hyd. Flat Tappet grind. Mark

 

Here is the reply from Cower Cams,

hydraulic flat tappet, 1.6 rockers

@.050 in. 232 / ex 238 computed power 444.32 @ 5000 rpm
lift .524 in. / .521 ex torque 581 80 @3973 rpm
108 LSA power range 1800 - 5000 rpm


@.050 in. 242* / ex .250 power 472.28 @ 5250 rpm
lift .543 in. / .548 ex torque 584.38 @ 4246 rpm
power range 2000 - 5500

Looks like 1.6 roller rockers would be needed with this lobe lift . Adv Dur was 1# 292 / 298 & 2#302 / 308 , slow easy on the train profiles with tight LSA's what do you folks think ?

Thanks
ick

 

The first cam is close to what I was figuring and is what I would recommend.

There is something not right with their Power figure of 444 @ 5000 rpm
HP = Torque at 5252 rpm and if the HP is 444@ 5000 then the torque should around 430 @ 5252.
So if you look at the torque, 581 @ 3973, here it is 1250 rpms later at 430 for a 151 ft lb drop off.
That seem a lot for a BBB.
I would expect the peak torque to be lower and the peak power to be a little higher than what Crower is showing.

Take a look through these engine builds by JW.

http://www.v8buick.com/showthread.p...Builts-Parts-and-power-comparisions&highlight=

Anyway with a 108 LSA you have 19 degrees of overlap which is a pretty rough idle and borderline for intake manifold vacuum for power brakes.
It would be fine for a car doing a lot of track time.
Also with that much overlap a 3000 stall converter would probably be needed.
But it's up to you and what will work for you.

I would ask them to recalculate using a 110 LSA and compare.

The second cam is way too big.

The stock rocker will give you .508/.505 lift which is good with the easy lobe ramps.

If you have to go to a 1.6 roller rocker then I would ask them for more lift.
It would be a waste to spend the money on the TA rockers for only a .524 lift.

Paul

 

Is 276 a lot of cranking compression?

 

The lobe seperation is 106* on the big Mama cam from Crower. It's just to dam big for my use for sure ! Here is there smaller grind >232* - 238* .508'' .505'' @ 1.55 rocker ratio 108* LSA. pmuller9 would widen LSA to 110* & use a .335 lobe lift that would yield .519'' @ 1.55 rocker ratio, & with the light spring pressures & slow lobe profiles I think I can get away with the stock rockers. I am going to run this by Dave Crower & see what he has to say. Crowers service has been outstanding & they seem to have a sense of humor "big Mama" & also told me that if these arn't to my liking he would crank out another one @ half price .

 

We had a problem with a Crane cam and needed a custom billet 50mm roller in time so we could make the last race of the season.
We called them Monday and they had the cam to our shop that Friday. Great service!

Paul

 

Here are 2 grinds That have been kicking around 232*/236* .505/.516 lift on a 110*lsa 14* overlap& 232*/240* .505/.516 on a 110*lsa 16* overlap

the first cam usesEZ follower lobe profiles on both in. & ex.
The second uses EZ follower only on the intake lobe profile & not on the exhust (not listed for the .240 lobe) All these lobes use spring pressures of 100 - 125# seat & 280 - 300# open.
Anyone ever use this EZ lobe ?

Mark